"This is one of the most elusive and mysterious outbreaks we've encountered," Center for Veterinary Medicine Director Bernadette Dunham said in the FDA release. "Our beloved four-legged companions deserve our best effort, and we are giving it."

With no known leads as to what is causing the sickness, the FDA is asking consumers to be wary when feeding pets treats.

Owners are also encouraged to reduce the amount of dog treats given to pets because "treats are a treat" and not a "necessary part of a fully-balanced diet," according to an FDA consumer fact sheet.

Since 2011, more than 1,200 treats have been tested for contaminants known to cause symptoms and illnesses reported in pets including salmonella, metals, pesticides and antibiotics. Trace amounts of antibiotics have been found on some treats but they are negligible according to the FDA and likely not a cause for the mystery illness.

Hoping to prevent future cases, some retailers launched self-imposed recalls in January due to the antibiotic residue found on treats. While the FDA claims the antibiotics are not an issue, recalls on brands like Nestle Purina Pet Care Co's Waggin Train and Del Monte's Milo's Kitchen Chicken Jerky have had positive effects none the less.

The recall has put fewer treats on the market which may be part of the reason under 400 jerky-related illness cases have been reported in 2013, the first notable decline since the link between illness and the treats was made in 2007.

The FDA has also inspected the facilities in China that produce the jerky treats in question but, like the lab tests, no cause of illness could be identified. Now, the organization is launching an investigation into the ingredient supply chain with regulators in China.

An effected pet is likely to display symptoms such as decreased appetite, decreased activity, vomiting, diarrhea and increased urination that, if untreated, could lead to death.

The problem has mainly impacted dogs but ten cats have also fallen ill. No cat deaths have been reported to date.